scanner: get rid of leaks

Free all the memory we have allocated during running.

v2.: split creating objects and getting rid of leaks
     into two patches

     move check for NULL description into free_description

v3.: rebase after previous patch fixes

Signed-off-by: Marek Chalupa <mchqwerty@gmail.com>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>